In many electrical systems, a need may arise to increase the voltage potential applied to elements within the system. This need may arise for many reasons including, for example, power source considerations, load considerations, and power transmission considerations. For example, in the automotive industry, need currently exists to increase the electrical power capability for future vehicles caused by design considerations associated with reducing fuel consumption and the introduction of new and/or improved electrical features and devices. In some situations, new power networks must be sized to accommodate increased energy demands associated with new devices designed and implemented for comfort, security, and safety in addition to servicing the electrical needs of major systems such as braking, electric power steering and suspension systems. In consideration of demands from the marketplace, it is contemplated that the electrical potential of some direct current (DC) systems may be increased from the currently common level of between 6 and 15 volts to significantly higher levels, such as between 20 and 60 volts. Many systems currently under consideration for the automotive industry rely upon a potential of 42 volts. It is contemplated that higher voltage systems, and subsystems, may be devised in the future.
The introduction of such increased voltage systems, for example, systems with potentials exceeding approximately 20 volts, however, causes considerable additional component and system modifications to ensure the reliability and electrical safety of such systems. More specifically, the impact of an increased voltage in an electrical system that utilizes a forty-two volt, direct current network, is to require attention to be focused on the arcing phenomenon that can occur within electrical distributions systems and components. It should be noted that such electrical arcing may occur as a result of cut, pinched or chaffed wiring. Accordingly, a need exists to develop systems and methods for preventing and detecting arcing within such systems, which may include, for example, wire harnesses within automotive, aerospace, appliance, medical instruments or other such devices where electrical arcing is to be avoided.
In the instance of a wire being cut or broken under an electrical load, an arc may be drawn across the gap created by the break or cut, between the exposed ends of the wire. Such an arc is often undesirable, its effects may not have been considered, and no provision may have been made to enable its extinction. In many cases, severe damage may occur if such an arc is sustained. It should be noted that, as used herein, the term “series arc fault” refers to arc faults that occur when an arc is situated in series with a load. Hot unplugs that may be caused by loose connections are often series arc faults. Unfortunately, however, series arc faults cannot typically be cleared by fuses or circuit breakers.
Arc faults in parallel to the load are identified as parallel arc faults. An example of parallel arc faults can be damaged wires drawing an arc to a ground potential, such as a chassis of an automobile. In an electrical system, the insulation jacket of one or more wires might become broken due to aging, mishandling, or damage (e.g., shaved, chaffed or pinched cable jackets). In such cases, an arc fault may be created, causing a temporary short circuit. The arc fault current, however, may thermally over-load and damage contacts within the circuit due to low contact force, resulting in melting and evaporating contact material, which may be followed by still more arcing. The arc fault current, which is typically related to, and limited by, the circuit impedance and the arc voltage, can be significantly lower than the trip current of the protection device, such as the fuse or circuit breaker. As a result, the time required for clearing the fault often depends on the time or current characteristics of the system and may not occur until too late, if at all.
While this disclosure makes extensive use of examples drawn from the automobile, it should understood that both the needs described herein and the inventive solutions disclosed are applicable to many other fields of use such as the aerospace industry, manufacturing equipment, recreational vehicles, medical equipment, appliances, arc-welding equipment, and any other field where an electrical device may encounter electrical arcing—especially devices utilizing DC sources of voltage. It should be noted that vehicles, especially flight vehicles, may require additional considerations due their associated weight and reliability considerations. It should be understood that electrical arcing may occur even at low voltages, and the effects of such arcing, and the importance of its detection and/or prevention depends upon the system and environment in which the arc occurs. The ability of individual systems to withstand arcing may depend highly upon the specifics of the system. For example, where an electrical system is to be exposed to an extremely volatile substance, such as within a fuel tank of an aircraft or other vehicle, electrical arcing may be extremely serious, and must be mitigated—regardless of the voltage potential of the system.
Consequently, there remains a need in the art for arc detection and protection systems and methods, primarily for DC circuits, capable of rapidly detecting parallel arcs and/or series arcs. It would be beneficial to have a system and method capable of distinguishing unwanted and unplanned arcs from expected or tolerated transient arcs, such as those that might be expected to be caused by the opening of a load switch. It would be further beneficial to be able to utilize arc detection components, such as sensors and the like, that are sufficiently compact to enable them to be incorporated in devices such as electrical connectors, junction blocks, relays, circuit breakers, and the like. It would also be desirable to have a system and method for continuously monitoring for arcing conditions rather than periodically sampling. It would further be desirable to have an arc detection and protection system that uses low cost components without requiring the use of microprocessors or complex algorithms.